The difference between parties and movements is simple: Parties are loyal to their own power regardless of policy agenda; movements are loyal to their own policy agenda regardless of which party champions it. This is one of the few enduring political axioms, and it explains why the organizations purporting to lead an American progressive "movement" have yet to build a real movement, much less a successful one.
Though the 2006 and 2008 elections were billed as progressive movement successes, the story behind them highlights a longer-term failure. During those contests, most leaders of Washington's major labor, environmental, anti-war and anti-poverty groups spent millions of dollars on a party endeavor-specifically, on electing a Democratic president and Democratic Congress. In the process, many groups subverted their own movement agendas in the name of electoral unity.
The effort involved a sleight of hand. These groups begged their grass-roots members-janitors, soccer moms, veterans and other "regular folks"-to cough up small-dollar contributions in return for the promise of movement pressure on both parties' politicians. Simultaneously, these groups went to dot-com and Wall Street millionaires asking them to chip in big checks in exchange for advocacy that did not offend those fat cats' Democratic politician friends (or those millionaires' economic privilege).
This wasn't totally dishonest. Many groups sincerely believed that Democratic Party promotion was key to progressive movement causes. And anyway, during the Bush era, many of those causes automatically helped Democrats by indicting Republicans.